Device for the transmission of short electromagnetic waves, especially for highest frequency tubes



May 7, 1968 P. KAHL. ET AL 3,382,466

DEVICE FOR THE TRANSMISSION OF SHORT ELECTROMAGNETIC WAVES, ESPECIALLY FOR HIGHEST FREQUENCY TUBES Filed Sept. 24, 1955 United States Patent 5 Claims. Cl. 333-98 ABSTRACT OF THE DISCLOSURE A window structure for a high power traveling wave tube comprising a thin-walled elongated tube of copper secured vacuum tight at one end thereof with an annular copper flange, and at the other, free end thereof with a solid ring of Vacon, which is within such free end and surrounded thereby, the ring of Vacon framing a ceramic plate window.

The invention relates to a device for the transmission of short electromagnetic waves, especially tubes, for highest-frequencies, with a hollow conductor and a highfrequency permeable, dielectric window or diaphragm, which extends over a coupling aperture of the hollow conductor and is arranged on an elastic tubular metal part, by means of which the window is connected vacuumtight with an annular metal flange serving for attachment to the hollow conductor.

There are already known coupling devices, for the high-frequency connection of highest-frequency apparatus with a hollow conductor, which contain so-called uncoupling windows. Such uncoupling windows consist of a dielectric material and extend across a coupling aperture of the highest-frequency apparatus on which borders the hollow conductor, having a corresponding aperture. It is also a known practice, in this connection, to provide between the connection of the window and the highestfrequency apparatus, an intermediate piece which is sufficiently flexible that movements of the window-like part, during the production or operation of the highest-frequency apparatus, are absorbed by the intermediate piece.

In the known coupling arrangements mentioned, the intermediate piece is disposed at a location at which substantially no high-frequency field is present. Use is made of this measure in order, on the one hand, to avoid the use of a low-loss material for the intermediate piece, and, on the other hand to afford suflicient space for a fastening arrangement which will accommodate expansion between the window and the intermediate piece. Resulting, however, from the fact, that the connection of the window-like part with the highest-frequency apparatus is disposed outside the highest frequency fields, the window itself must be relatively large. Moreover, difliculties of a technological nature result, if the window is to be arranged as near as possible to the coupling aperture of the highest-frequency apparatus, which is desired in many cases, for reason of high-frequency technology.

The invention therefore has as its problem that of providing a coupling device for the transmission of short electromagnetic waves, especially for a high frequency connection of a highest-frequency tube of high output with a hollow conductor, in which a reliable vacuumtight closure of the device is achievable with a windowlike part having relatively small space requirements. For the solution to this problem, in a device of the type initially mentioned, it is proposed that the tubular metal portion consist of an electrically low-loss material with the same coeflicient of expansion as the metal of the 3,382,466 Patented May 7, 1968 annular flange, and at its free end encompasses a solid metal ring, whose coeflicient of expansion is substantially equal to the coefficient of expansion of material of the dielectric window.

In a device according to the invention preferably both the flange ring and the tubular metal part are fabricated of copper, since, as is Well known, copper is a low-loss material from a viewpoint of high frequency technology, and simultaneously possesses very good properties from the viewpoint of vacuum technology. Furthermore, the use of copper as the material for the tubular metal part has, the special advantage that by reason of the ductility of copper, a suitably thin-walled copper tube possesses sufficient elasticity, without necessitating the use of further structural measures. The solid metal ring which is surrounded by the free end of the copper tube, preferably is contracted of a material comprising an iron-nickelcobalt alloy. Such alloys, as is well known, enable, in the temperature ranges concerned, a sufficient accommodation of expansion in the dielectric media of ceramic material utilized in vacuum-tight coupling windows. The solid metal ring advantageously, is provided with at least one circularly shaped corrugation-like indentation whereby the bending moment is reduced at the connection be tween the metal ring and the copper tube.

The invention will hereinafter be explained in detail with the aid of the example of construction illustrated in the drawing.

Referring to the drawing, reference numeral 1 designates a disc of dielectric material, particularly ceramic material, which is disposed within and soldered to a solid ring 2 of so-called Vacon (an iron-nickel-cobalt alloy) to form a vacuum-tight connection, in which arrangement the ring 2 is provided with a bead-like circular groove adjacent the soldered connection to the ceramic disc. The thin-walled copper tube 3, which is suitably connected, for example, by soldering, to an annularly flanged member 4, which likewise is preferably constructed of copper, the free end of said tubular member encircling the ceramic disc 1, including the Vacon ring 2, with the latter likewise being soldered, in vacuum-tight relation, to the copper tube 3.

The annularly flanged member 4, illustrated in the drawing, preferably is part of the vacuum shell of a highest-frequency tube, for example a traveling wave tube. The aperture 5 in the member 4 thus constitutes the coupling aperture of the tube, which is sealed, vacuum tight, by the high-frequency permeable ceramic disc 1. The annularly flanged member 4 is adopted to be connected, in known manner to a hollow wave guide with a corresponding flanged member in which arrangement the longitudinal axis of the hollow wave guide can extend parallel to the coupling aperture 5.

The window structural element illustrated in the drawing, consisting of the copper tube 3, the Vacon ring 2, and the ceramic disc 1, is ordinarily separately produced and first of all examined for mechanical faults, the vacuum-tightness being tested simultaneously under an applied temperature, and only after such testing is such structural element soldered to the annularly flanged member 4. Experiments have indicated that no mechanical tension stresses occur at the metal-ceramic-solder-junction between the disc 1 and the ring 2, either in the soldering of the window structure element, or in the operation of a cooperable traveling wave tube. At the same time, the copper tube 3 is so elastic that no movements of the ceramic part 1 and of the metal ring 2 are transmitted to the flanged member 4.

It was possible to determine that an annularly flanged member, into which the structural element referred to had been soldered, was not deformed. On the other hand, when a known-type annular metal part, constructed of an iron-nickel alloy, was employed, there resulted a bulging of the flanged copper member 4 on the order of tenths of millimeters.

The invention is not restricted to the example of construction illustrated. In particular, the tubular metal part 3 can be constructed with an integral connection to the annula'rly flanged member 4.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim as our invention:

1. A device for the transmission of short electromagnetic waves, especially for highest-frequency tubes with a hollow conductor, and a high-frequency permeable dielectric window which extends across a coupling aperture of the hollow conductor and is arranged on a tubular elastic metal part, by means of which the window is connected in vacuum-tight relation with an annularlyflanged metal member forming the means of attachment to the ,hollow conductor, characterized in that the tubular elastic metal part is formed from an electrically low-loss material with a coefiicient of expansion substantiallyequal to that of the metal of the annularly flanged member, and connected to the flanged member in vacuum tight relation, said annularly flanged metal memberhaving a cylindrical wall portion and a transverse wall portion, said'tubular elastic metal part having one end thereof secured to the inner face of said transverse wall portion and having the tubular Walls thereof spaced from the cylindrical wall portion of said annularly flanged metal member, and

a solid metal ring, in which said window is secured in vacuum-tight relation, disposed in the free end of said tubular metal part, and having its peripheral face connected to said free end in vacuum-tight relation, the inner peripheral face of the free end of the tubular metal part surrounding and overlying said peripheral face of said solid metal ring, and said tubular metal part having a wall thickness and a length to provide substantial elasticity, for absorbing forces exerted thereon by said dow is constructed of an aluminum oxide ceramic.

4. A device according to claim 2, wherein'said metal ring has at least one annular indentation in the proximity of the connection of the ceramic window with said ring.

5. A device according to claim 4, wherein the window comprises a disc-like plate disposed, with said metal ring in a common plane.

References Cited UNITED STATES PATENTS 2,958,834 11/1960 Symons et al. 333-98 FOREIGN PATENTS 1/1956 Australia.

OTHER REFERENCES Ragan, G. L., Microwave Transmission Circuits, N0. 9, Radiation Laboratory Series, McGraw-Hill, 1948, pp. 220-222 relied on.

Pryslak, N. E., Metal-to-Ceramic Seals for Magner tron Waveguides,

in Electronics, January 1954, pp. 282 287 relied on.

HERMAN KARL SAALBACH, Primary Examiner.

L. ALLAHUT, Assistant Examiner. 

